This invention relates to improvements in an apparatus for detecting a rotational or angular phase of a camshaft relative to a crankshaft and an apparatus for calculating an intake air quantity of a cylinder by using a detected value of the camshaft rotational phase, in an engine provided with a variable valve timing control mechanism.
A variable valve timing control mechanism for an engine has been hitherto known and configured such that the opening and closing timings of intake and exhaust valves are controlled by varying the rotational phase of a camshaft relative to a crankshaft under a hydraulic pressure. The engine provided with the valve timing control mechanism of this type is usually equipped with a crank angle sensor and a cam angle sensor. The crank angle sensor is adapted to output a crank angle signal every a predetermined angle (for example, 10xc2x0 in crank angle) in synchronism with rotation of the crankshaft. The cam angle sensor is adapted to produce a cam angle signal every a predetermined angle (for example, 180xc2x0 in crank angle) in synchronism with rotation of the cam shaft. In accordance with the crank angle signal and the cam angle signal, the rotational phase (so-called VTC phase) of the camshaft relative to the crank shaft is detected to be used for carrying out a variety of engine controls.
Drawbacks have been encountered in the above technique for detecting the camshaft rotational phase, as set forth below. That is, there is only a detected value of the VTC phase as information at a prior time until the crank angle signal and the cam angle signal are output. However, the actual VTC phase may change by a considerable amount during a time period from a prior time detection of the VTC phase and the current time. Particularly when the engine is stopped under idling stop or the like, detection of the VTC phase cannot be carried out until the crank angle signal and the cam angle signal are again detected upon re-starting of the engine. As a result, a feedback control for the VTC phase cannot be accomplished at a high accuracy.
Additionally, also in case that the mass of air to be sucked into a cylinder is calculated by using a cylinder volume (volume of air) calculated in accordance with the opening and closing timings of the intake and exhaust valves, a control cannot follow the cylinder volume which varies in accordance with the closing timing of the intake valve. As a result, the mass of air to be sucked into the cylinder cannot be calculated at a high accuracy, and therefore a fuel injection control and an air-fuel ratio control for the engine cannot be accomplished at a high accuracy.
Therefore, it is an object of the present invention is to provide an improved camshaft rotational phase detecting apparatus and a cylinder intake air quantity calculating apparatus which can overcome drawbacks encountered in conventional camshaft rotational phase detecting apparatuses and cylinder intake air quantity calculating apparatuses.
Another object of the present invention is to provide an improved camshaft rotational phase detecting apparatus which can estimate an actual rotational phase of a camshaft relative to a crankshaft even in case that the rotational phase cannot be detected, thereby carrying out a variety of controls for an engine at a high accuracy.
A further object of the present invention is to provide an improved cylinder intake air quantity calculating apparatus by which a quantity of air to be sucked into a cylinder of an engine can be effectively calculated even in a condition where the rotational phase of the camshaft cannot be detected or in case that measuring error become large.
An aspect of the present invention resides in a camshaft rotational phase detecting apparatus for an engine provided with a variable valve timing control mechanism which controls a camshaft rotational phase of an engine valve to a target camshaft rotational phase by varying a rotational phase of a camshaft relative to a crankshaft. The camshaft rotational phase detecting apparatus is configured to detect a camshaft rotational phase as a detected camshaft rotational phase based on a signal from a sensor. In the apparatus, the detected camshaft rotational phase is substituted with a maintained rotational phase for a predetermined period and is substituted with a target camshaft rotational phase after a lapse of the predetermined period, when the camshaft rotational phase is not detected. In the apparatus, the maintained rotational phase is set corresponding to the detected camshaft rotational phase detected before a timing that the camshaft rotational phase is not detected. Additionally, in the apparatus, the predetermined period is set in accordance with an engine temperature.
Another aspect of the present invention resides in a camshaft rotational phase detecting apparatus for an engine provided with a variable valve timing control mechanism which controls a camshaft rotational phase of an engine valve by varying a rotational phase of a camshaft relative to a crankshaft. The camshaft rotational phase detecting apparatus is configured to perform detecting a camshaft rotational phase as a detected camshaft rotational phase based on a signal from a sensor, wherein the detected camshaft rotational phase is substituted with a corrected rotational phase when the camshaft rotational phase is not detected. In the apparatus, the corrected rotational phase is provided by correcting the detected camshaft rotational phase detected before a timing that the camshaft rotational phase is not detected, with an engine temperature and an elapsed time from the timing becoming the condition that the camshaft rotational phase is not detected.
A further aspect of the present invention resides in a camshaft rotational phase detecting apparatus for an engine provided with a variable valve timing control mechanism which controls a camshaft rotational phase of an engine valve by varying a rotational phase of a camshaft relative to a crankshaft. The camshaft rotational phase detecting apparatus is configured to perform detecting a camshaft rotational phase based on output of a sensor, wherein the camshaft rotational phase at this time when an engine speed is below a predetermined level is substituted with the camshaft rotational phase which is detected at last time.
A still further aspect of the present invention resides in a cylinder intake air quantity calculating apparatus for an engine. The apparatus comprises a detecting section that detects a camshaft rotational phase as a detected camshaft rotational phase based on a signal from a sensor. In the apparatus, the detected camshaft rotational phase is substituted with a maintained rotational phase for a predetermined period and is substituted with a target camshaft rotational phase after a lapse of the predetermined period, when the camshaft rotational phase is not detected. In the apparatus, the maintained rotational phase is set corresponding to the detected camshaft rotational phase which is detected before a timing that the camshaft rotational phase is not detected. Additionally, the apparatus further comprises a calculating section that calculates a mass air quantity sucked into a cylinder in accordance with the detected camshaft rotational phase derived from the detecting section.
A still further aspect of the present invention resides in a cylinder intake air quantity calculating apparatus for an engine. The apparatus comprises a detecting section that detects a camshaft rotational phase as a detected camshaft rotational phase based on an output from a sensor, wherein the detected camshaft rotational phase is substituted with a corrected rotational phase when the camshaft rotational phase is not detected. In the apparatus, the corrected rotational phase is provided by correcting the detected camshaft rotational phase detected before a timing that the camshaft rotational phase is not detected, with an engine temperature and an elapsed time from the timing becoming the condition that the camshaft rotational phase is not detected. Additionally, the apparatus further comprises a calculating section that calculates a mass air quantity sucked into a cylinder in accordance with the detected camshaft rotational phase derived from the detecting section.